In German Published Patent Appln. No. 44 45 359, a sensor is described for detecting combustible gases. The sensor includes a substrate having two printed conductors having comb-type interlacing at their head ends. In the area of the interlaced ends, a sensitive semiconducting metal oxide layer is applied over the printed conductors. The sensitive semiconducting metal oxide layer can have a spongelike structure, or can be fashioned as a composite of grains sintered together.